A modelling approach to the detection of subcutaneous tumours by haematoporphyrin-derivative fluorescence

The possibility of subcutaneous tumour detection by haematoporphyrin-derivative (HPD) and light has been studied by calculations on a model. The tumour model consists of a skin layer and a (subcutaneous) tumour layer. The Kubelka-Munk theory has been applied to estimate the HPD fluorescence intensities from the two layers. Literature values have been used for the optical parameters of the tissues. The results are that the depth at which a subcutaneous tumour can be detected is almost independent of the excitation wavelength and the tumour thickness. Only superficial tumours (less than 2.3 mm subcutaneously) can be detected as HPD fluorescence from the overlying skin tends to become more intense than from the tumour.